Conventionally, touch panels have been used commonly as one kind of input device that receives an input operation from a user. Such a touch panel is disposed on the front face of a display unit such as a Liquid Crystal Display (LCD) and waits for a touching operation (a contact, etc.) to be given by a user's finger or a touch pen (a stylus or the like) in a state that the display unit displays a target image (e.g., a button image). When an area (a reception area) on the touch panel that corresponds to the button image is touched, the input device enters instruction information, etc. assigned to the touched button image.
Recently, compact devices such as portable game devices, mobile phones (portable terminals), etc. have come to carry a touch panel. In general, users hold such a compact device in one hand and give a touching operation to the touch panel by the other hand (a finger or a touch pen), often resulting in that the user's finger or the like shakes and misses the point. When giving a touching operation with a touch pen, users often let it slip on the touch panel to be out of position.
When a touching operation is given to an edge (boundary) of the button image on the touch panel, the finger or the like that has touched down might shake, coming into and out of the reception area repeatedly, raising a concern that determination of an input might run an intermittent repetition of ON and OFF (i.e., there occurs a chattering).
A disclosed technique for appropriately preventing occurrence of such a chattering detects any touch to the touch panel, and in response, expands the reception area (recognition area) of the touched button image within an extent that it does not overlap other reception areas to perform determination based on the position of the finger or the like when it is detached (released) from the touch panel and the expanded reception area (e.g., see Patent Literature 1).    Patent Literature 1: Unexamined Japanese Patent Application KOKAI Publication No. 2006-133887 (pp. 5-10, FIG. 5)